Atopy is a predisposition toward developing certain allergic hypersensitivity reactions. Atopy may have a hereditary component, although contact with the allergen or irritant must occur before the hypersensitivity reaction can develop.
As of 2012, 63.9 percent of players playing in Major League Baseball are white. There is no way of telling the exact number due to the number of players.
On September 1, the active player limit for MLB baseball teams expands from 25 to 40 players.